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Astron. Astrophys. 347, 169-177 (1999)


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Classification and spectral analysis of faint central stars of highly excited planetary nebulae *

T. Rauch 1, J. Köppen 2, R. Napiwotzki 3 and K. Werner 1

1 Institut für Astronomie und Astrophysik der Universität, D-72076 Tübingen, Germany
2 URA1280, Observatoire Astronomique, 11, rue de l'université, F-67000 Strasbourg, France
3 Dr. Remeis-Sternwarte, Universität Erlangen-Nürnberg, D-96049 Bamberg, Germany

Received 25 January 1999 / Accepted 12 April 1999

Abstract

We present narrow-band images of nine planetary nebulae (PN) and a spectral analysis of four of their central stars (CSPN) by means of model atmosphere techniques based on medium-resolution optical spectra.

Four of our CSPN are unambiguously identified. They are very hot ([FORMULA] [FORMULA]) and have about 1 - 2 times solar He/H abundance ratios. (the exciting stars of PN G214.9+07.8, PN G231.8+04.1, PN G283.6+25.3, PN G293.6+10.9).

Three other of our PN are candidates for Abell 35-like objects: The supposed central stars of PN G257.5+00.6 and PN G277.1-03.8 exhibit F-type spectra while probably the hotter exciting star escapes detection in the optical. Absorption features is the spectrum of the central star of PN G283.6+25.3 suggest the presence of a cool companion.

The images of PN G277.1-03.8 display two close stars at its center which both show F-type spectra. It appears likely that this is a binary system but better spectra and additional UV spectra are required in order to successfully identify the exciting central star.

Key words: stars: abundances – stars: AGB and post-AGB – stars: atmospheres – stars: evolution – ISM: planetary nebulae: general

* Based on observations collected at the European Southern Observatory, La Silla, Chile (proposals 56.D-0717, 57.D-0148)

Send offprint requests to: T. Rauch

Correspondence to: rauch@astro.uni-tuebingen.de

© European Southern Observatory (ESO) 1999

Online publication: June 18, 1999

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